U.S. Pat. No. 4,024,857 discloses a device for collecting a small quantity of capillary blood from a puncture site in the ear, finger, or other portion of a patient's body. Since the anticoagulated blood so collected and stored may then be used for microhematological procedures which by general definition involve quantities of 100 microliters (.mu.l) or less, the device is disclosed and generally marketed as a micro blood collector. It consists essentially of a vial of rigid polymeric material, a vented cap which has a capillary tube for drawing the blood sample by gravity into the vial, and in the commercial form, a plug to replace the cap for the purpose of sealing the vial after a blood sample has been taken.
Replacement of the cap by the plug is essential if the vial is to be sealed because, in addition to providing a capillary tube, the cap is also vented. The vent is in turn required in order to allow the escape of air as the vial is filled with blood under the influence of gravity and capillary action. Therefore, following the drawing of a sample, a user must replace the cap with the plug in order to mix the sample with anticoagulant already present in the vial and to prevent contamination or loss of the contents of the vial during subsequent storage and handling.
As a practical matter, even further manipulation is required because of the need or desirability for supplying such a vial to the user in sealed condition. Such a vial is ordinarily supplied with a measured quantity of anticoagulant and one or more mixing beads and, to protect such contents, the vial is prefitted with the replacement plug. Thus, as part of the manipulative procedure, the user must first remove the plug and substitute the capillary cap and then, after the sample is drawn, remove the cap and replace the plug. Such manipulative steps are cumbersome, timeconsuming, and clearly undesirable not only because they increase the risks of contamination of the blood sample but also because they increase the chances that the user might accidentally touch the blood sample and become contaminated by pathogens in that sample.
Other patents indicating the state of the art are U.S. Pat. Nos. 3,902,477, 3,181,529, 3,513,829, 3,718,133, 3,322,114, and 2,655,152.